With the rapid development of wireless communication and micro-electromechanical technologies in recent years, wireless sensing networks have found wide applications in various different fields. In a wireless sensing network, sensing apparatuses distributed over the sensing network are responsible for collecting various data (e.g., the occurrence of events, environment data being sensed periodically, etc.), while a main control apparatus analyzes the data collected by the sensing apparatuses. Since the time instant that the data is collected/sensed by the sensing apparatus tends to have a major influence on the result of the analysis, it is crucial whether the main control apparatus can obtain the correct time instant that the data is sensed.
In conventional wireless sensing networks, the main control apparatus obtains the correct time instant that the data is sensed mainly in three ways. In the first way, the sensing apparatuses are connected to the Internet to obtain accurate time instants via the network time protocol and then synchronize time with the main control apparatus. However, the main control apparatus is vulnerable to the Distributed Denial of Service (DDoS) attack if the first way is adopted. The second way is to configure a Global Positioning System (GPS) module inside the sensing apparatuses, and the third way is to configure a time synchronization chip inside the sensing apparatuses. However, the sensing apparatuses will become oversized in volume and have a high cost no matter whether the second or the third way is adopted.
Accordingly, an urgent need exists in the technical field of wireless sensing networks to provide a time alignment mechanism, through which the sensing apparatuses will not have a high cost and will not become oversized and the main control apparatus will not be vulnerable to the network attack.